Observation of Long-Range Elliptic Azimuthal Anisotropies in sqrt[s]=13 and 2.76 TeV pp Collisions with the ATLAS Detector

ATLAS has measured two-particle correlations as a function of the relative azimuthal angle, Δϕ, and pseudorapidity, Δη, in sqrt[s]=13 and 2.76 TeV pp collisions at the LHC using charged particles measured in the pseudorapidity interval |η|<2.5. The correlation functions evaluated in different intervals of measured charged-particle multiplicity show a multiplicity-dependent enhancement at Δϕ∼0 that extends over a wide range of Δη, which has been referred to as the "ridge." Per-trigger-particle yields, Y(Δϕ), are measured over 2<|Δη|<5. For both collision energies, the Y(Δϕ) distribution in all multiplicity intervals is found to be consistent with a linear combination of the per-trigger-particle yields measured in collisions with less than 20 reconstructed tracks, and a constant combinatoric contribution modulated by cos(2Δϕ). The fitted Fourier coefficient, v_{2,2}, exhibits factorization, suggesting that the ridge results from per-event cos(2ϕ) modulation of the single-particle distribution with Fourier coefficients v_{2}. The v_{2} values are presented as a function of multiplicity and transverse momentum. They are found to be approximately constant as a function of multiplicity and to have a p_{T} dependence similar to that measured in p+Pb and Pb+Pb collisions. The v_{2} values in the 13 and 2.76 TeV data are consistent within uncertainties. These results suggest that the ridge in pp collisions arises from the same or similar underlying physics as observed in p+Pb collisions, and that the dynamics responsible for the ridge has no strong sqrt[s] dependence.

Measurement of the ZZ Production Cross Section in pp Collisions at sqrt[s]=13 TeV with the ATLAS Detector

The ZZ production cross section in proton-proton collisions at 13 TeV center-of-mass energy is measured using 3.2  fb^{-1} of data recorded with the ATLAS detector at the Large Hadron Collider. The considered Z boson candidates decay to an electron or muon pair of mass 66-116 GeV. The cross section is measured in a fiducial phase space reflecting the detector acceptance. It is also extrapolated to a total phase space for Z bosons in the same mass range and of all decay modes, giving 16.7_{-2.0}^{+2.2}(stat)+0.9/-0.7(syst)+1.0/-0.7(lumi)  pb. The results agree with standard model predictions.

Determination of the Ratio of b-Quark Fragmentation Fractions f(s)/f(d) in pp Collisions at √s=7 TeV with the ATLAS Detector

With an integrated luminosity of 2.47  fb(-1) recorded by the ATLAS experiment at the LHC, the exclusive decays B(s)(0)→J/ψϕ and B(d)(0)→J/ψK(*0) of B mesons produced in pp collisions at √s=7  TeV are used to determine the ratio of fragmentation fractions f(s)/f(d). From the observed B(s)(0)→J/ψϕ and B(d)(0)→J/ψK(*0) yields, the quantity (f(s)/f(d))[B(B(s)(0)→J/ψϕ)/B(B(d)(0)→J/ψK(*0))] is measured to be 0.199±0.004(stat)±0.008(syst). Using a recent theory prediction for [B(B(s)(0)→J/ψϕ)/B(B(d)(0)→J/ψK(*0))] yields (f(s)/f(d))=0.240±0.004(stat)±0.010(syst)±0.017(th). This result is based on a new approach that provides a significant improvement of the world average.

Search for Dark Matter in Events with Missing Transverse Momentum and a Higgs Boson Decaying to Two Photons in pp Collisions at sqrt[s]=8 TeV with the ATLAS Detector

Results of a search for new phenomena in events with large missing transverse momentum and a Higgs boson decaying to two photons are reported. Data from proton-proton collisions at a center-of-mass energy of 8 TeV and corresponding to an integrated luminosity of 20.3 fb^{-1} have been collected with the ATLAS detector at the LHC. The observed data are well described by the expected standard model backgrounds. Upper limits on the cross section of events with large missing transverse momentum and a Higgs boson candidate are also placed. Exclusion limits are presented for models of physics beyond the standard model featuring dark-matter candidates.

Measurements of the Total and Differential Higgs Boson Production Cross Sections Combining the H→γγ and H→ZZ^{*}→4ℓ Decay Channels at sqrt[s]=8 TeV with the ATLAS Detector

Measurements of the total and differential cross sections of Higgs boson production are performed using 20.3  fb^{-1} of pp collisions produced by the Large Hadron Collider at a center-of-mass energy of sqrt[s]=8  TeV and recorded by the ATLAS detector. Cross sections are obtained from measured H→γγ and H→ZZ^{*}→4ℓ event yields, which are combined accounting for detector efficiencies, fiducial acceptances, and branching fractions. Differential cross sections are reported as a function of Higgs boson transverse momentum, Higgs boson rapidity, number of jets in the event, and transverse momentum of the leading jet. The total production cross section is determined to be σ_{pp→H}=33.0±5.3 (stat)±1.6 (syst)  pb. The measurements are compared to state-of-the-art predictions.

Search for a Heavy Neutral Particle Decaying to eμ, eτ, or μτ in pp Collisions at sqrt[s]=8 TeV with the ATLAS Detector

This Letter presents a search for a heavy neutral particle decaying into an opposite-sign different-flavor dilepton pair, e^{±}μ^{∓}, e^{±}τ^{∓}, or μ^{±}τ^{∓} using 20.3  fb^{-1} of pp collision data at sqrt[s]=8  TeV collected by the ATLAS detector at the LHC. The numbers of observed candidate events are compatible with the standard model expectations. Limits are set on the cross section of new phenomena in two scenarios: the production of ν[over ˜]_{τ} in R-parity-violating supersymmetric models and the production of a lepton-flavor-violating Z^{'} vector boson.

Evidence of Wγγ Production in pp Collisions at sqrt[s]=8 TeV and Limits on Anomalous Quartic Gauge Couplings with the ATLAS Detector

This Letter reports evidence of triple gauge boson production pp→W(ℓν)γγ+X, which is accessible for the first time with the 8 TeV LHC data set. The fiducial cross section for this process is measured in a data sample corresponding to an integrated luminosity of 20.3  fb^{-1}, collected by the ATLAS detector in 2012. Events are selected using the W boson decay to eν or μν as well as requiring two isolated photons. The measured cross section is used to set limits on anomalous quartic gauge couplings in the high diphoton mass region.

Search for a new resonance decaying to a W or Z boson and a Higgs boson in the [Formula: see text] final states with the ATLAS detector

A search for a new resonance decaying to a W or Z boson and a Higgs boson in the [Formula: see text] final states is performed using 20.3 fb[Formula: see text] of pp collision data recorded at [Formula: see text] 8 TeV with the ATLAS detector at the Large Hadron Collider. The search is conducted by examining the WH / ZH invariant mass distribution for a localized excess. No significant deviation from the Standard Model background prediction is observed. The results are interpreted in terms of constraints on the Minimal Walking Technicolor model and on a simplified approach based on a phenomenological Lagrangian of Heavy Vector Triplets.

Search for Scalar Charm Quark Pair Production in pp Collisions at sqrt[s]=8 TeV with the ATLAS Detector

The results of a dedicated search for pair production of scalar partners of charm quarks are reported. The search is based on an integrated luminosity of 20.3  fb^{-1} of pp collisions at sqrt[s]=8  TeV recorded with the ATLAS detector at the LHC. The search is performed using events with large missing transverse momentum and at least two jets, where the two leading jets are each tagged as originating from c quarks. Events containing isolated electrons or muons are vetoed. In an R-parity-conserving minimal supersymmetric scenario in which a single scalar-charm state is kinematically accessible, and where it decays exclusively into a charm quark and a neutralino, 95% confidence-level upper limits are obtained in the scalar-charm-neutralino mass plane such that, for neutralino masses below 200 GeV, scalar-charm masses up to 490 GeV are excluded.

Measurement of spin correlation in top-antitop quark events and search for top squark pair production in pp collisions at √s=8 TeV using the ATLAS detector

A measurement of spin correlation in tt[over ¯] production is presented using data collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 20.3  fb^{-1}. The correlation between the top and antitop quark spins is extracted from dilepton tt[over ¯] events by using the difference in the azimuthal angle between the two charged leptons in the laboratory frame. In the helicity basis the measured degree of correlation corresponds to A_{helicity}=0.38±0.04, in agreement with the standard model prediction. A search is performed for pair production of top squarks with masses close to the top quark mass decaying to predominantly right-handed top quarks and a light neutralino, the lightest supersymmetric particle. Top squarks with masses between the top quark mass and 191 GeV are excluded at the 95% confidence level.

Search for Higgs and Z Boson Decays to J/ψγ and ϒ(nS)γ with the ATLAS Detector

A search for the decays of the Higgs and Z bosons to J/ψγ and ϒ(nS)γ (n=1,2,3) is performed with pp collision data samples corresponding to integrated luminosities of up to 20.3  fb^{-1} collected at sqrt[s]=8  TeV with the ATLAS detector at the CERN Large Hadron Collider. No significant excess of events is observed above expected backgrounds and 95% C.L. upper limits are placed on the branching fractions. In the J/ψγ final state the limits are 1.5×10^{-3} and 2.6×10^{-6} for the Higgs and Z boson decays, respectively, while in the ϒ(1S,2S,3S)γ final states the limits are (1.3,1.9,1.3)×10^{-3} and (3.4,6.5,5.4)×10^{-6}, respectively.

Search for Higgs boson pair production in the γγbb[over ¯] final state using pp collision data at sqrt[s]=8 TeV from the ATLAS detector

Searches are performed for resonant and nonresonant Higgs boson pair production in the γγbb[over ¯] final state using 20  fb^{-1} of proton-proton collisions at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the CERN Large Hadron Collider. A 95% confidence level upper limit on the cross section times branching ratio of nonresonant production is set at 2.2 pb, while the expected limit is 1.0 pb. The difference derives from a modest excess of events, corresponding to 2.4 standard deviations from the background-only hypothesis. The limit observed in the search for a narrow X→hh resonance ranges between 0.7 and 3.5 pb as a function of the resonance mass.

Measurements of the Nuclear Modification Factor for Jets in Pb+Pb Collisions at √(s)NN]=2.76 TeV with the ATLAS detector

Measurements of inclusive jet production are performed in pp and Pb+Pb collisions at √(s)NN=2.76  TeV with the ATLAS detector at the LHC, corresponding to integrated luminosities of 4.0 and 0.14  nb(-1), respectively. The jets are identified with the anti-k(t) algorithm with R=0.4, and the spectra are measured over the kinematic range of jet transverse momentum 32<p(T)<500  GeV and absolute rapidity |y|<2.1 and as a function of collision centrality. The nuclear modification factor R(AA) is evaluated, and jets are found to be suppressed by approximately a factor of 2 in central collisions compared to pp collisions. The R(AA) shows a slight increase with p(T) and no significant variation with rapidity.

Observation of an excited Bc(±) meson state with the ATLAS detector

A search for excited states of the Bc(±) meson is performed using 4.9  fb(-1) of 7 TeV and 19.2  fb(-1) of 8 TeV pp collision data collected by the ATLAS experiment at the LHC. A new state is observed through its hadronic transition to the ground state, with the latter detected in the decay Bc(±)→J/ψπ(±). The state appears in the m(Bc(±)π(+)π(-))-m(Bc(±))-2m(π(±)) mass difference distribution with a significance of 5.2 standard deviations. The mass of the observed state is 6842±4±5  MeV, where the first error is statistical and the second is systematic. The mass and decay of this state are consistent with expectations for the second S-wave state of the Bc(±) meson, Bc(±)(2S).

Measurement of the [Formula: see text] production cross-section using [Formula: see text] events with [Formula: see text]-tagged jets in [Formula: see text] collisions at [Formula: see text] and 8 TeV with the ATLAS detector

The inclusive top quark pair ([Formula: see text]) production cross-section [Formula: see text] has been measured in proton-proton collisions at [Formula: see text] and [Formula: see text] with the ATLAS experiment at the LHC, using [Formula: see text] events with an opposite-charge [Formula: see text] pair in the final state. The measurement was performed with the 2011 7 TeV dataset corresponding to an integrated luminosity of 4.6 [Formula: see text] and the 2012 8 TeV dataset of 20.3 [Formula: see text]. The numbers of events with exactly one and exactly two [Formula: see text]-tagged jets were counted and used to simultaneously determine [Formula: see text] and the efficiency to reconstruct and [Formula: see text]-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section was measured to be: [Formula: see text]where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, knowledge of the integrated luminosity and of the LHC beam energy. The results are consistent with recent theoretical QCD calculations at next-to-next-to-leading order. Fiducial measurements corresponding to the experimental acceptance of the leptons are also reported, together with the ratio of cross-sections measured at the two centre-of-mass energies. The inclusive cross-section results were used to determine the top quark pole mass via the dependence of the theoretically predicted cross-section on [Formula: see text] giving a result of [Formula: see text][Formula: see text] GeV. By looking for an excess of [Formula: see text] production with respect to the QCD prediction, the results were also used to place limits on the pair-production of supersymmetric top squarks [Formula: see text] with masses close to the top quark mass, decaying via [Formula: see text] to predominantly right-handed top quarks and a light neutralino [Formula: see text], the lightest supersymmetric particle. Top squarks with masses between the top quark mass and 177 GeV are excluded at the 95 % confidence level.

Measurement of the [Formula: see text] production cross-section using [Formula: see text] events with [Formula: see text]-tagged jets in [Formula: see text] collisions at [Formula: see text] and 8 TeV with the ATLAS detector

The inclusive top quark pair ([Formula: see text]) production cross-section [Formula: see text] has been measured in proton-proton collisions at [Formula: see text] and [Formula: see text] with the ATLAS experiment at the LHC, using [Formula: see text] events with an opposite-charge [Formula: see text] pair in the final state. The measurement was performed with the 2011 7 TeV dataset corresponding to an integrated luminosity of 4.6 [Formula: see text] and the 2012 8 TeV dataset of 20.3 [Formula: see text]. The numbers of events with exactly one and exactly two [Formula: see text]-tagged jets were counted and used to simultaneously determine [Formula: see text] and the efficiency to reconstruct and [Formula: see text]-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section was measured to be: [Formula: see text]where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, knowledge of the integrated luminosity and of the LHC beam energy. The results are consistent with recent theoretical QCD calculations at next-to-next-to-leading order. Fiducial measurements corresponding to the experimental acceptance of the leptons are also reported, together with the ratio of cross-sections measured at the two centre-of-mass energies. The inclusive cross-section results were used to determine the top quark pole mass via the dependence of the theoretically predicted cross-section on [Formula: see text] giving a result of [Formula: see text][Formula: see text] GeV. By looking for an excess of [Formula: see text] production with respect to the QCD prediction, the results were also used to place limits on the pair-production of supersymmetric top squarks [Formula: see text] with masses close to the top quark mass, decaying via [Formula: see text] to predominantly right-handed top quarks and a light neutralino [Formula: see text], the lightest supersymmetric particle. Top squarks with masses between the top quark mass and 177 GeV are excluded at the 95 % confidence level.

Search for scalar diphoton resonances in the mass range 65-600 GeV with the ATLAS detector in pp collision data at √s=8 TeV

A search for scalar particles decaying via narrow resonances into two photons in the mass range 65-600 GeV is performed using 20.3  fb(-1) of √s 8 TeV pp collision data collected with the ATLAS detector at the Large Hadron Collider. The recently discovered Higgs boson is treated as a background. No significant evidence for an additional signal is observed. The results are presented as limits at the 95% confidence level on the production cross section of a scalar boson times branching ratio into two photons, in a fiducial volume where the reconstruction efficiency is approximately independent of the event topology. The upper limits set extend over a considerably wider mass range than previous searches.

Evidence for electroweak production of W±W±jj in pp collisions at sqrt[s] = 8 TeV with the ATLAS detector

This Letter presents the first study of W(±)W(±)jj, same-electric-charge diboson production in association with two jets, using 20.3 fb(-1) of proton-proton collision data at sqrt[s] = 8  TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with two reconstructed same-charge leptons (e(±)e(±), e(±)μ(±), and μ(±)μ(±)) and two or more jets are analyzed. Production cross sections are measured in two fiducial regions, with different sensitivities to the electroweak and strong production mechanisms. First evidence for W(±)W(±)jj production and electroweak-only W(±)W(±)jj production is observed with a significance of 4.5 and 3.6 standard deviations, respectively. The measured production cross sections are in agreement with standard model predictions. Limits at 95% confidence level are set on anomalous quartic gauge couplings.

Measurements of four-lepton production at the Z resonance in pp collisions at sqrt[s] = 7 and 8 TeV with ATLAS

Measurements of four-lepton (4ℓ, ℓ=e,μ) production cross sections at the Z resonance in pp collisions at the LHC with the ATLAS detector are presented. For dilepton and four-lepton invariant mass regions m(ℓ+ℓ(-)) > 5 GeV and 80<m(4ℓ) < 100 GeV, the measured cross sections are 76 ± 18(stat) ± 4(syst) ± 1.4(lumi) fb and 107 ± 9(stat) ± 4(syst) ± 3.0(lumi) fb at sqrt[s] = 7 and 8 TeV, respectively. By subtracting the nonresonant 4ℓ production contributions and normalizing with Z → μ(+)μ(-) events, the branching fraction for the Z boson decay to 4ℓ is determined to be (3.20 ± 0.25(stat) ± 0.13(syst)) × 10(-6), consistent with the standard model prediction.

Search for quantum black hole production in high-invariant-mass lepton+jet final states using pp collisions at √s=8 TeV and the ATLAS detector

This Letter presents a search for quantum black-hole production using 20.3 fb-1 of data collected with the ATLAS detector in pp collisions at the LHC at √s = 8 TeV. The quantum black holes are assumed to decay into a final state characterized by a lepton (electron or muon) and a jet. In either channel, no event with a lepton-jet invariant mass of 3.5 TeV or more is observed, consistent with the expected background. Limits are set on the product of cross sections and branching fractions for the lepton+jet final states of quantum black holes produced in a search region for invariant masses above 1 TeV. The combined 95% confidence level upper limit on this product for quantum black holes with threshold mass above 3.5 TeV is 0.18 fb. This limit constrains the threshold quantum black-hole mass to be above 5.3 TeV in the model considered.

Search for dark matter in events with a hadronically decaying W or Z boson and missing transverse momentum in pp collisions at √s=8 TeV with the ATLAS detector

A search is presented for dark matter pair production in association with a W or Z boson in pp collisions representing 20.3  fb(-1) of integrated luminosity at √s=8  TeV using data recorded with the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet with the jet mass consistent with a W or Z boson, and with large missing transverse momentum are analyzed. The data are consistent with the standard model expectations. Limits are set on the mass scale in effective field theories that describe the interaction of dark matter and standard model particles, and on the cross section of Higgs production and decay to invisible particles. In addition, cross section limits on the anomalous production of W or Z bosons with large missing transverse momentum are set in two fiducial regions.

Measurement of top quark polarization in top-antitop events from proton-proton collisions at √s=7 TeV using the ATLAS detector

This Letter presents measurements of the polarization of the top quark in top-antitop quark pair events, using 4.7  fb(-1) of proton-proton collision data recorded with the ATLAS detector at the Large Hadron Collider at √s=7  TeV. Final states containing one or two isolated leptons (electrons or muons) and jets are considered. Two measurements of α(ℓ)P, the product of the leptonic spin-analyzing power and the top quark polarization, are performed assuming that the polarization is introduced by either a CP conserving or a maximally CP violating production process. The measurements obtained, α(ℓ)P(CPC)=-0.035±0.014(stat)±0.037(syst) and α(ℓ)P(CPV)=0.020±0.016(stat)(-0.017)(+0.013)(syst), are in good agreement with the standard model prediction of negligible top quark polarization.

Measurement of the azimuthal angle dependence of inclusive jet yields in Pb+Pb collisions at √(sNN)=2.76 TeV with the ATLAS detector

Measurements of the variation of inclusive jet suppression as a function of relative azimuthal angle, Δφ, with respect to the elliptic event plane provide insight into the path-length dependence of jet quenching. ATLAS has measured the Δφ dependence of jet yields in 0.14 nb(-1) of √(s(NN))=2.76 TeV Pb+Pb collisions at the LHC for jet transverse momenta p(T)>45 GeV in different collision centrality bins using an underlying event subtraction procedure that accounts for elliptic flow. The variation of the jet yield with Δφ was characterized by the parameter, v(2)(jet), and the ratio of out-of-plane (Δφ~π/2) to in-plane (Δφ~0) yields. Nonzero v(2)(jet) values were measured in all centrality bins for p(T)<160 GeV. The jet yields are observed to vary by as much as 20% between in-plane and out-of-plane directions.

Observation of associated near-side and away-side long-range correlations in sqrt[s(NN)]=5.02 TeV proton-lead collisions with the ATLAS detector

Two-particle correlations in relative azimuthal angle (Δø) and pseudorapidity (Δη) are measured in sqrt[s(NN)] = 5.02 TeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1 μb(-1) of data as a function of transverse momentum (p(T)) and the transverse energy (ΣE(T)(Pb)) summed over 3.1 < η < 4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2 < |Δ η | < 5) "near-side" (Δø ~ 0) correlation that grows rapidly with increasing ΣE(T)(Pb). A long-range "away-side" (Δø ~ π) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ΣE(T)(Pb), is found to match the near-side correlation in magnitude, shape (in Δη and Δø) and ΣE(T)(Pb) dependence. The resultant Δø correlation is approximately symmetric about π/2, and is consistent with a dominant cos2Δø modulation for all ΣE(T)(Pb) ranges and particle p(T).

Measurement of Z boson production in Pb-Pb collisions at sqrt[s(NN)]=2.76 TeV with the ATLAS detector

The ATLAS experiment has observed 1995 Z boson candidates in data corresponding to 0.15  nb(-1) of integrated luminosity obtained in the 2011 LHC Pb+Pb run at sqrt[s(NN)]=2.76  TeV. The Z bosons are reconstructed via dielectron and dimuon decay channels, with a background contamination of less than 3%. Results from the two channels are consistent and are combined. Within the statistical and systematic uncertainties, the per-event Z boson yield is proportional to the number of binary collisions estimated by the Glauber model. The elliptic anisotropy of the azimuthal distribution of the Z boson with respect to the event plane is found to be consistent with zero.

Search for dark matter candidates and large extra dimensions in events with a photon and missing transverse momentum in pp collision data at sqrt[s]=7 TeV with the ATLAS detector

Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum in proton-proton collisions at sqrt[s] = 7 TeV are reported. Data collected by the ATLAS experiment at the LHC corresponding to an integrated luminosity of 4.6 fb(-1) are used. Good agreement is observed between the data and the standard model predictions. The results are translated into exclusion limits on models with large extra spatial dimensions and on pair production of weakly interacting dark matter candidates.

Search for direct top squark pair production in final states with one isolated lepton, jets, and missing transverse momentum in sqrt[s] = 7 TeV pp collisions using 4.7 fb(-10 of ATLAS data

A search is presented for direct top squark pair production in final states with one isolated electron or muon, jets, and missing transverse momentum in proton-proton collisions at sqrt[s] = 7 TeV. The measurement is based on 4.7 fb(-1) of data collected with the ATLAS detector at the LHC. Each top squark is assumed to decay to a top quark and the lightest supersymmetric particle (LSP). The data are found to be consistent with standard model expectations. Top squark masses between 230 GeV and 440 GeV are excluded with 95% confidence for massless LSPs, and top squark masses around 400 GeV are excluded for LSP masses up to 125 GeV.

Search for a supersymmetric partner to the top quark in final states with jets and missing transverse momentum at sqrt[s] = 7 TeV with the ATLAS detector

A search for direct pair production of supersymmetric top squarks (t(1)) is presented, assuming the t(1) decays into a top quark and the lightest supersymmetric particle, χ(1)(0), and that both top quarks decay to purely hadronic final states. A total of 16 (4) events are observed compared to a predicted standard model background of 13.5(-3.6)(+3.7)(4.4(-1.3)(+1.7)) events in two signal regions based on ∫Ldt = 4.7 fb(-1) of pp collision data taken at sqrt[s] = 7 TeV with the ATLAS detector at the LHC. An exclusion region in the t(1) versus χ(1)(0) mass plane is evaluated: 370<m(t)(1)}<465 GeV is excluded for m(χ)(1)(0) ~ 0 GeV while m(t)(1) = 445 GeV is excluded for m(χ)(1)(0) ≤ 50 GeV.

Nutrients in urine: energetic aspects of removal and recovery

The analysis of different removal and recovery techniques for nutrients in urine shows that in many cases recovery is energetically more efficient than removal and new-production from natural resources. Considering only the running electricity and fossil energy requirements for the traditional way of wastewater treatment and fertiliser production, the following specific energy requirements can be calculated: 45 MJ kg(-1)N for denitrification in a WWTP, 49 MJ kg(-1)p for P-precipitation in a WWTP, 45 MJ kg(-1)N for N-fertiliser and 29 MJ kg(-1)p for P-fertiliser production. These numbers are higher than the values derived for thermal volume reduction of urine (35 MJ kg(-1)N for eliminating 90% water) or production of struvite (102 MJ kg(-1)N, including 2.2 kg P). Considering only the electricity and fossil energy for the traditional way of wastewater treatment and fertiliser production, the energy value of 1 PE urine is 0.87 MJ PE(-1) d(-1) (fertiliser value: 0.44, wastewater treatment: 0.43 MJ PE(-1) d(-1)). A more detailed life cycle assessment (LCA) of the entire urine collection system, including the required materials and the environmental burden, support the energy analysis. The LCA compares conventional denitrification in a wastewater treatment plant with collecting urine in households, reducing the volume by evaporation and using it as a multi-nutrient fertiliser. The primary energy consumption for recovery and reuse of urine, including the nutrients N, P and K, is calculated with 65 MJ kg(-1)N, compared with 153 MJ kg(-1)N derived for the conventional 'recycling over the atmosphere'.